Well, let's look at the Mincer Blades in particular since you brought them up.

When you go to attack in melee with a unit that has Mincer Blades as an upgrade, you'll do your normal attacks (it's easiest if you go ahead and see if they wound too), and then you'll do the Mincer Blade attacks.

Roll a d6 for each Mincer Blade in the unit to determine how many attacks you get with them. Roll that many dice (kept apart from your normal attacks) to see how many hit. Then, any of those that hit get Crushing Strength (2) to determine if they wound.

Add all of your inflicted wounds for that round together, then proceed to the Nerve test.